To develop nanotech therapies for cancer, it would be useful to be able to follow the distribution of nanoparticles in the patient to see if they are in fact accumulating in the targeted tumor(s). A noninvasive Raman microscope has allowed scientists to track carbon nanotubes injected into living mice. From the National Cancer Institute’s Alliance for Nanotechnology in Cancer “Seeing Nanotubes Targeting Tumors In Vivo“:

Carbon nanotubes have significant potential for delivering both imaging and therapeutic agents to tumors, but there is still a need to better quantify how well these rolled-up sheets of graphite can target tumors. Now, thanks to the development of a microscope capable of measuring Raman spectroscopic signals from living mice, researchers have a noninvasive tool to study where carbon nanotubes travel once they are injected into the blood stream.

Reporting its work in the journal Nano Letters [abstract], a team of investigators led by Sanjiv Gambhir, M.D., Ph.D., principal investigator of the Center for Cancer Nanotechnology Excellence Focused on Therapy Response (CCNE-TR), based at Stanford University, and Hongjie Dai, Ph.D., also a member of the CCNE-TR, described its use of an optimized Raman microscope to track two different sets of carbon nanotubes as they transited through the body of living mice. One of the nanotubes was covered with the tumor-targeting peptide known as RGD; the other set was used without any added functionality.

…Using this Raman microscope, the investigators were able to track differences in nanotube trafficking between the targeted and untargeted nanotubes. Although both sets of nanotubes showed an initial spike in tumor accumulation, the concentration of untargeted nanotubes in tumors began dropping as early as 20 minutes after injection. In contrast, the tumor concentration of the targeted nanotubes remained elevated for at least 72 hours after injection. In animals treated with the targeted nanotubes, tumors were readily visible as early as 2 hours postinjection and for at least 72 hours.

Not mentioned in either the NCI article or in the abstract is the question of how deep inside the body tissues can be imaged by the Raman microscope. If the microscope can penetrate a couple centimeters, for example, essentially all of a mouse but only the outermost tissue of a human could be imaged.—Jim